Candidate miRNAs Involved in Regulation of Alpha-class Glutathione S-transferases Associated with Susceptibility to the Carcinogen Aflatoxin B1

Glutathione S-transferases (GSTs) are critical enzymes that detoxify reactive electrophilic intermediates of environmental toxicants, such as mycotoxin aflatoxin B₁ (AFB₁), an hepatotoxic, carcinogenic, and immunosuppressive feed contaminant. Domesticated turkeys (Meleagris gallopavo) are the most sensitive animals known to AFB₁, at least partly due to their lack of AFB₁-detoxifying alpha-class GSTs (GSTA). Wild turkeys, which are relatively AFB₁-resistant, possess functional GSTAs. Evidence suggests this dysfunction likely results from differences in epigenetic gene regulation rather than DNA coding sequence. One possible epigenetic mechanism for GSTA silencing in domesticated turkeys is miRNA-mRNA interactions, but it is not known which of the 950 unique miRNAs identified or predicted in the turkey genome interact with GSTA mRNAs. We used RNA-sequencing (RNA-seq) data from turkey livers, with and without exposure to AFB₁, to identify precursor miRNAs with relative expression patterns expected for miRNAs involved in GSTA regulation. A subset of those miRNAs also have expression patterns that differ between domesticated and wild turkeys or predicted interactions (using Starmir) at single nucleotide polymorphisms (SNPs) between domesticated and wild turkey GSTA mRNAs, making them possible candidates to explain the AFB₁-susceptibility difference. Experimental validation of interactions between these 13 candidate miRNAs and GSTA mRNAs will employ anti-AGO RNA immunoprecipitation to determine whether any are responsible for GSTA dysfunction in domesticated turkeys. Supported by USDA, Agriculture and Food Research Initiative Grants # 2002-35204-12294, 2005-01326, 2007-35205-17880, 2009-35205-05302, and Grant #2013-01043 from the USDA-National Institute of Food and Agriculture Animal Genome Program, and the Utah Agricultural Experiment Station.